A. Field of the Invention
This invention relates to the field of towed vehicles which have many hydraulically operated functions and in particular, an electrohydraulic system for those hydraulic functions.
B. Prior Art
Towed vehicles are well known in the art in which specific functions are carried out hydraulically. In particular, towed farm vehicles may have from three to eight and even more functions each of which is hydraulically powered. For example, the "Stackeze" made by the Haybuster Corporation handles hay and has five functions and thus requires a control valve assembly with five hydraulic control valves and five control handles. Another towed farm vehicle, the "Mark 660 Potato Harvester" made by the Lockwood Corporation may have up to eight functions thus requiring at least one control valve assembly comprised of eight hydraulic control valves and eight control handles.
In such towed vehicles, the control valve assembly may be secured to the towed vehicle. Thus, an operator additional to the tractor operator is required to ride on the towed vehicle in order to actuate the control handles. On the other hand, the control valve assembly may be unbolted from the towed vehicle and attached to the tractor so that the control handles may be close to the tractor operator. Thus, it has been attempted to position the control valve assembly convenient to the tractor operator so that he could not only drive the tractor but also operate the controls of the valve assembly.
However, such "attachable" control valve assemblies have left much to be desired since each valve assembly requires many hydraulic lines between valve assembly and towed vehicle. Accordingly, with two hydraulic lines required for each function, the resultant valve assembly has been unwieldy as well as being a source of noise and dangerous hot oil close to the driver. In addition, the control handles have not really been convenient for manipulation from the driver's seat of the tractor. This is a particularly important problem since many farm tractors now have fully enclosed cabs to protect the operator from noise, dirt, heat, cold, etc. As a result, it has been extremely difficult for the operator to reach around out of the door of an enclosed cab in an attempt to operate the control handles. In some cases, the operator has had to open a window of the cab or make special large openings in the cab for this purpose. However, all of this defeats the purpose of an enclosed cab to provide the operator with a controlled and protected environment.
In an attempt to overcome these difficulties, it has been known to install the control valve assembly inside the cab. However, this is very undesirable. Such an installation requires that all the hydraulic hoses be brought into the cab. This almost completely defeats the controlled environment of the cab by bringing in heat from hoses carrying hot oil and hydraulic noise from the hydraulic system. Thus, there is the unacceptable danger to the operator from hot oil leaks which may be in violation of proposed OSHA regulations.
A further problem arises whether the valve assembly is within the cab or secured to the tractor outside the cab. Specifically, when the towed vehicle is released, the valve assembly must be unbolted, removed from the tractor and stowed on the towed vehicle. Thus there has been required a very heavy transfer of a valve assembly and hydraulic lines with the resultant breakage and crimping of the hydraulic lines.